check with the science teachers too. Sometimes they are already prepared for this kind of stuff.
Dont forget the game i havent seen in years. Take a bowl with a lid that can't be seen threw. Put in grapes (eyeballs), spaghetti ( snakes?), but with it being covered they will never know and if you make it a game, the one that guesses the most of the weird stuff you can find in a lab, wins a small prize.
We had a Mad Scientist's Lab at our Harvest Hoopla one year and some of the things might work for you...
We had a couple of microscopes and a couple of specimens for the kids to look at. One was a spider, so they could see all of the eyes and such. The other was a fly and they could see the wings, hair, etc. The kids really likes that...
We also had one of those electricity orbs. It looked really cool in the black lighting room, but could still work for what you are trying to do. The kids likes being able to touch it and see our they became conduits for the electricity... Something that you might be able to do is play around with static electricy. Get some of the kids hair to stick up...
If I was to try to do something like this at a classroom level I would see if a dad would be willing to come in a dress up as the mad scientist. See if there is someplace within the school that could be used for this so that the room could be set up before hand and the kids could be brought to the room with a sign hanging saying "Beware, Mad Scientist's Lab". Have the room all neon and black lighting. The mad scientist can wear a white lab coat, glasses, etc. There is even neon gel that our "actor" used. Or you can purchase one of those rubber hair pieces that makes the person look bald in the middle with white hair sticking up on either side... Maybe have a couple of assitants that can run different stations. There are many different types of experiements that the mad scientist can perform safely. You could still have the snacks and such as well. I'm sure that some pretty cool experiments could be found online...
I have found myself in charge of my daughter's 3rd grade Halloween class party. I'm thinking of going with a "Mad Scientist" theme and doing hands-on science activities and "make it and take it" stuff instead of just sitting around and eating stuff. Any ideas for activities or games? I looked on Steve Spangler Science.com and found some ideas, but I would appreciate any help!